Cant get I2C LCD working

Hello,
Hooked up a new 20x4 I2C lcd pannel as in the described in the irrigation controller drawing (A4 & A5, PWR, and GND). Used the fmalpartida-new-liquidcrystal-bb6d545c00c3 library form GITHUB, but cant get Hello World working. Changed LCD Address to 0x20. Any other place to find a library?

@y4CdW42Ol8
Let me be more specific. I have the 20x4 line LCD connected to a Arduino DUE using 5v, GND, A4 > SDA, and A5 > SCL. The back light come on when power is ON, and that's it. I have successfully compiled the Blinking Cursor and Hello World examples in the MySensory I2C libary (changing: LiquidCrystal_I2C lcd(0x20, 20, 4); because my LCD A0-A2 not jumpered). But nothing happens on the LCD. The LED on the small I2C board is ON. The DUE is working, since I have run other sketches.

What could I be doing wrong? A bad LCD? Bad PINS on the DUE? How do I change the PIN numbers on the DUE.

Some other Examples in the LiquidCrystal_I2C library use the following:

Is there a jumper on the two pins at the other end of the serial board on the back? My most recent ones came withOUT those and I get no back-light or red-LED on the serial board until I put a jumper on them.

Most if not all of these LCD modules are based off of the older parallel 44780 based LCDs. This is probably a clone or very similar. I am guessing that the potentiometer is the contrast control. double check that in the documentation for the I2C board that is on the back, but if it is, you may need to turn that up or down to get your unit to display. If there is no documentation, look at the I2C board on the back. It should connect to a 16 pin header connector. For the 44780 LCDs it was pin 3 that was the contrast pin. The pot just created a voltage divider that went from 0(GND) to +5V. If you can trace the pins on the pot, you should see one going to GND or pin 1 on the header, 1 to +5V or pin 2 on the header, and the other one to the contrast pin 3 of the header. If that all checks, then that is for sure your contrast control.http://www.learningaboutelectronics.com/Articles/Arduino-HD44780-circuit.php